Dementia is a chronic organic mental disorder, characterised by the following main clinical features:

  1. Impairment of intellectual functions,
  2. Impairment of memory (predominantly of recent memory, especially in early stages),
  3. Deterioration of personality with lack of personal  care.

Impairment of all these functions occurs globally, causing interference with day-to-day activities and interpersonal relationships. There is impairment of judgement and impulse control, and also impairment of abstract thinking. There is however usually no impairment of consciousness (unlike in delirium; see Table: A Comparison of Delirium and Dementia ). The course of dementia is usually progressive though some forms of dementia can be reversible.


[Table : A Comparison of Delirium and Dementia]

Features Delirium Dementia
1. Onset Usually acute Usually insidious
2. Course Usually recover in 1 week; may take up to 1 month Usually protracted, although may be reversible in some cases
3. Clinical features
a.Consciousness Clouded Usually normal
b.Orientation Grossly disturbed Usually normal ; disturbed only in late stages
c.Memory Immediate retention and recall disturbed

Recent memory disturbed

Immediate retention and recall normal

Recent memory disturbed
Remote memory disturbed only in late stages

d.Comprehension Impaired Impaired only in late stages
e.Sleep-wake cycle Grossly disturbed Usually normal
f.Attention and concentration Grossly disturbed Usually normal
g. Diurnal variation Marked; sundowning may be present Usually absent
h. Perception Visual illusions and  hallucinations very common Hallucinations may occur
i. Other features Asterixis; multifocal myoclonus Catastrophic reaction; perseveration

Additional features may also be present. These include:

  1. Emotional lability (marked variation in emotional expression).
  2. Catastrophic reaction (when confronted with an assignment which is beyond the residual intellectual capacity, patient may go into a sudden rage).
  3. Thought abnormalities, e.g. perseveration, delusions.
  4. Urinary and faecal incontinence may develop in later stages.
  5. Disorientation in time; disorientation in place and person may also develop in later stages.
  6. Neurological signs may or may not be present, depending on the underlying cause.


Like delirium, the diagnosis of dementia is clinical though ancillary laboratory investigations may help in elucidating the underlying aetiology.
According to ICD-10, the following features are required for diagnosis: evidence of decline in both memory and thinking, suffi cient enough to impair personal activities of daily living, memory impairment(typically affecting registration, storage, and retrieval of new information though previously learned material may also be lost particularly in later stages, impaired
thinking, presence of clear consciousness (consciousness can be impaired if delirium is also present), and a duration of at least 6 months.

The following conditions must be kept in mind in the differential diagnosis of dementia.

1. Normal aging process:

Although impairment of  memory and intellect are commoner in elderly, their mere presence does not justify a diagnosis of dementia. Dementia is diagnosed only when there is demonstrable evidence of memory and other intellectual impairment which is of sufficient severity to interfere with social and/or occupational functioning. The normal memory impairment in old age is called as benign senescent forgetfulness.

2. Delirium:

The syndromes of delirium and dementia may overlap. See Table: A Comparison of Delirium and Dementia for a comparison of clinical features.

3. Depressive pseudodementia:

Depression in the elderly patients may mimic dementia clinically. It is called as depressive pseudodementia (Table : Dementia vs Pseudodementia). Identifi cation of depression is very important as it is far more easily treatable than dementia.

[Table : Dementia vs Pseudodementia]

Dementia Pseudodementia (Depressive)
1. Patient rarely complains of cognitive impairment Patient usually always complains about memory impairment
2. Patient often emphasises achievements Patient often emphasises disability
3. Patient often appears unconcerned Patient very often communicates distress
4. Usually labile affect Severe depression on examination
5. Patient makes errors on cognitive examination ‘Do not know’ answers are more frequent
6. Recent memory impairment found on examination Recent memory impairment rarely found on examination
7. Confabulation may be present Confabulation very rare
8. Consistently poor performance on similar tests Marked variability in performance on similar tests
9. History of depression less common Past history of manic and/or depressive episodes may be present

The depressed patients often complain of memory impairment, diffi culty in sustaining attention and concentration, and reduced intellectual capacity. In contrast, patients with dementia do not often complain of these disturbances. In fact, when confronted with evidence of memory impairment, they often confabulate. As depression may often be superimposed on dementia, it is at times necessary to undertake a therapeutic trial with antidepressants, if the clinical picture is unclear.

It is useful to differentiate dementia into cortical and subcortical subtypes (Table).

Table 3.5: Cortical and Subcortical Dementia

Features Cortical Dementia Subcortical Dementia
1.Site of lesion Cortex (frontal and temporoparieto-occipital association areas, and hippocampus) Subcortical grey matter (thalamus, basal ganglia, and rostral brain stem)
2.Examples Alzheimer’s disease, Pick’s disease Huntington’ chorea, Parkinson’s disease,
Progressive supranuclear palsy, Wilson’s disease
3.Severity Severe Mild to moderate
4. Motor system Usually normal Dysarthria, flexed/extended posture,
tremors, dystonia, chorea, ataxia, rigidity
5.Other features Simple delusions; depression uncommon; severe aphasia, amnesia, agnosia, apraxia, acalculia, slowed cognitive speed (bradyphrenia) Complex delusions; depression common; rarely mania
6.Memory deficit (Short-term) Recall helped very little by cues Recall partially helped by cues and recognition tasks


A large number of conditions can cause dementia.

A. Parenchymatous brain disease

Alzheimer’s disease, Pick’s disease, Parkinson’s  disease, Huntington’s chorea, Lewy body dementia, Steel Richardson syndrome ( Progressive Supranuclear Palsy)

B. Vascular dementia

Multi-infarct dementia, subcortical vascular dementia ( Binswanger’s disease)

C. Toxic dementias

Bromide intoxication, drugs, heavy metals, alcohol, carbon monoxide, analgesics, anticonvulsants, benzodiazepines,
psychotropic drugs

D. Metabolic dementias

Chronic hepatic or uraemic encephalopathy, dialysis dementia, Wilson’s disease

E. Endocrine causes

Thyroid, parathyroid, pituitary, adrenal dysfunction

F. Deficiency dementias

Pernicious anaemia, pellagra, folic acid defi ciency, thiamine defi ciency

G. Dementias due to infections

Creutzfeldt-Jacob disease, neurosyphilis, chronic meningitis, viral encephalitis, AIDS dementia, other
HIV-related disorders, sub acute sclerosing panencephalitis (SSPE)

H. Neoplastic dementias

Neoplasms and other intracranial space-occupying  lesions

I. Traumatic dementias

Chronic subdural haematoma, head injury

J. Hydrocephalic dementia

Normal pressure hydrocephalus

Clinically important types

However, a majority of cases are due to a few common causes such as Alzheimer’s disease and multi-infarct dementia. Some clinically important types of dementia are briefly discussed here.

Alzheimer’s Dementia

This is the commonest cause of dementia, seen inabout 70% of all cases of dementia in USA. It is more commonly seen in women. Earlier, it was differentiated into two forms: a presenile form and a senile form. Now it is known that these two forms represent the same disease clinically and pathologically. There is some evidence to suggest that Alzheimer’s disease may have a genetic basis.
The diagnosis of Alzheimer’s dementia is by exclusion of all other causes of dementia, as there are no distinct diagnostic clinical features or laboratory investigations. Autopsy shows macroscopic changes such as enlarged cerebral ventricles, widened cerebral sulci and shrinkage of cerebral cortex, as well as microscopic changes such as senile plaques, neurofibrillary tangles, cortical nerve cell loss, and granulovacuolar degeneration. However, these changes are only quantitatively, and not qualitatively, different from a normal aged brain. Neurochemically, there is a marked decrease in brain choline acetyltransferase (CAT) with a similar decrease in brain acetylcholinesterase (AchE).

At present, Alzheimer’s dementia is not considered a treatable disorder. However, Cholinesterase Inhibitors such as Rivastigmine (1.5 mg twice a day to 6 mg twice a day), Donepezil (5-10 mg/day), and Galantamine (4 mg twice a day to 12 mg twice a day) have been used in the recent past for treatment of moderate dementia with Alzheimer’s disease. These elevate acetylcholine (Ach) concentrations in cerebral cortex by slowing the degradation of acetylcholine released by still intact cholinergic neurons in  Alzheimer’s disease.

Memantine (5-20 mg/day), an N-methyl-D-aspartate (NMDA) antagonist, is also available for the treatment of moderately severe to severe Alzheimer’s disease. There are several other drugs (such as ginkgo biloba, piracetam, and vitamin C and E) used for treatment, though their value remains uncertain.

Multi-infarct Dementia

Multi-infarct dementia is the second commonest cause of dementia, seen in 10-15% of all cases, though some studies indicate that multi-infarct dementia is probably far more common in India. It is also one of the important treatable causes of dementia.

Occurrence of multiple cerebral infarctions can lead to a progressive disruption of brain function, leading to dementia. The most typical form of multi-infarct dementia is characterised by the following features:

  1. An abrupt onset,
  2. Acute exacerbations (due to repeated infarctions),
  3.  Stepwise clinical deterioration (step-ladder pat-tern),
  4. Fluctuating course,
  5. Presence of hypertension (most commonly) or any other significant cardiovascular disease, and
  6. His tory of previous stroke or transient ischemic attacks (TIAs).

Focal neurological signs are frequently present. Insight into the illness is usually present in the early part of the course. Emotional lability is common. EEG (showing focal area of slowing) and brain imaging (CT scan or MRI scan of brain showing multiple infarcts) help in diagnosis. The treatment of the underlying cause can prevent further deterioration by preventing further infarctions.

Hypothyroid Dementia

This has been considered one of the most important treatable and reversible causes of dementia, second only to toxic dementias. Although it accounts for less than 1% of dementias, hypothyroidism should be suspected in every patient of dementia.

Since clinical diagnosis of hypothyroid dementia may be diffi cult, laboratory tests should be used for correct diagnosis. Prompt treatment can reverse the dementing process and can lead to complete recovery if the treatment is star ted within two years of the onset of dementia.

AIDS Dementia Complex

About 50-70% of patients suffering from AIDS exhibit a triad of cognitive, behavioural and motoric deficits of subcortical dementia type and this is known as the AIDS-dementia complex (ADC). Dementia can in fact be an initial presentation in about 25% cases of AIDS.

As the AIDS virus (a lenti-virus, a type of retrovirus) is highly neurotropic and the virus crosses the blood-brain barrier early in the course of the disease cognitive impairment is nearly ubiquitous in AIDS. The diagnosis is established by ELISA (enzyme linked immuno-sorbent assay) showing anti-HIV antibodies, and the Western
Blot test (blotting of antibody specifi cities to HIV-specific proteins). A Cranial CT scan can show cortical atrophy 1-4 months before the onset of clinical dementia while MRI scan is helpful in detecting the white matter lesions.

Lewy Body Dementia

Lewy body dementia is now believed to be the second most common cause of the degenerative dementias, accounting for about 4% of all dementias. Typically, the clinical features of Lewy body dementia include:

  1. Fluctuating cognitive impairment over weeks or months, with involvement of memory and higher cortical functions (such as language, visuospatial ability, praxis and reasoning). Lucid intervals can be present in between fluctuations.
  2. Recurrent and detailed visual hallucinations.
  3. Spontaneous extrapyramidal or parkinsonian  symptoms such as rigidity and tremors.
  4. Neuroleptic sensitivity syndrome, characterised by  a marked sensitivity to the effects of typical doses of antipsychotic drugs (resulting in severe extrapyramidal side-effects with use of antipsychotics).

Other clinical features may include repeated falls, autonomic dysfunction (e.g. orthostatic hypotension), urinary incontinence, delusions and depressive features. Although Lewy bodies (intracytoplasmic inclusion bodies) are also present in Parkinson’s disease, the occurrence of Lewy bodies in Lewy body dementia is more widespread. A PET (Positron Emission Tomography) or SPECT (Single Photon Emission Computerised Tomography) scan of brain may show low dopamine transporter uptake in basal ganglia.

Antipsychotic medication should be avoided (or used with extreme caution and in low doses) in patients with Lewy body dementia.


Basic Investigations

The diagnostic tests are of great importance in finding the cause, or to exclude all other causes before diagnosing Alzheimer’s dementia.

The list of investigations could include

  • complete blood count,
  • urinalysis,
  • blood glucose,
  • serum electrolytes,
  • renal function tests,
  • thyroid function tests,
  • serum B12 and folate levels,
  • serological tests for syphilis,
  • arterial pO2 and pCO2
  • X-ray chest,
  • ECG,
  • X-ray skull,
  • EEG,
  • lumbar puncture,
  • CT scan/MRI scan of brain,
  • neuropsychological tests, and
  • drug screens.

Treatment of the Underlying Cause, if Treatable

Some underlying causes of dementia are treatable (reversible dementias), for example,

  • treatment of hypertension in multi-infarct dementia,
  • thyroxin replacement in hypothyroid dementia,
  • shunting in hydrocephalic dementia,
  • levodopa in parkinsonism, and
  • removal of the toxic agent in toxic dementias.

Early treatment can prevent further deterioration of dementia.

Symptomatic Management

  1. Environmental manipulation and focus on coping skills to reduce stress in day-to-day activities.
  2. Treatment of medical complications, if any.
  3. Care of food and hygiene
  4. Supportive care for the patient and family/carers.
  5. Anxiety symptoms can be treated with low dose of  a short-acting benzodiazepine (such as Lorazepam and Oxazepam), though care should be taken to prevent benzodiazepine dependence/misuse.
  6. Depression can be treated with low doses of SSRIs such as Citalopram or Sertraline as these antidepressants have low anticholinergic activity and have a safer cardiac profi le. Agents with high anticholinergic activity can cause confusion or even frank delirium.
  7. Psychotic symptoms and disruptive behaviours can be treated with low doses of antipsychotics. Haloperidol and Risperidone have usually been preferred as they are less sedating and have low cardiac toxicity, though Risperidone can cause postural hypotension. Recently, the use of antipsychotics in treatment of behavioural symptoms in dementia has decreased markedly due to possible association of antipsychotic use with increased mortality. Antipsychotics should also be avoided if Lewy body dementia is suspected.
  8. Short-term hospitalisation may be needed for emergent symptoms whilst a longer term hospitalisation or respite placement may be necessary in later stages. Specifi c drug treatment such as cholinesterase inhibitors (e.g. donepezil, rivastigmine, galantamine) in moderate  Alzheimer’s disease, or memantine (NMDA antagonist) in moderate to severe Alzheimer’s disease, can be helpful.
No Comments

Leave a Comment